Shaft Diameter in an Old Air Pump

[Leon bee]

I'm gonna restore an old portable compressor we pulled out of a friend's pile. It seems to be a kit that goes with one of those WW2 bomber oxygen tanks. I need the big pulley for the pump, looks like a 5/8" shaft but no matter how many times I measure it, comes out .65 something. So, like 21/32". And I never heard of this. The little pump could be war surplus, it looks like it says "T.P. CO. MADE IN USA". Guess we can ream out a 5/8 pulley hub, but I'm curious if anybody has an idea about this. Thanks!

 

[RoninB4]

-This is a WAG so don't put too much credibility in it. Sometimes an oddball size can either mean it was an individual project and that's what was on hand to finish the project. Or it was an attempt at capturing business by using a proprietary/oddball item that was only available from one source, theirs. The use of proprietary/oddball thread designations (TPI or thread form) was encountered now and then, especially on expensive equipment.

 

[Leon bee]

Thanks, Ronin. Not a very important mystery, I guess.

 

[RoninB4]

Thanks, Ronin. Not a very important mystery, I guess.

-It doesn't have to be important to deserve an answer. Glad to help.

 

[RTM]

-This is a WAG so don't put too much credibility in it. Sometimes an oddball size can either mean it was an individual project and that's what was on hand to finish the project. Or it was an attempt at capturing business by using a proprietary/oddball item that was only available from one source, theirs. The use of proprietary/oddball thread designations (TPI or thread form) was encountered now and then, especially on expensive equipment.

Another thought or two, they were building these for airplane use, correct? Maybe they were working to a weight limit, and that weird size saved them the 1# they needed, and still get the strength.

Or a cost cap, and someone was closing out that size.

Not serious here: Or the machinist fell asleep at the switch, and turned it down too far?

 

[Leon bee]

I doubt if the little pump was for aircraft, but don't know. It's cast iron. Those tanks were everywhere in the 50s it seems. This seems like a kit made just for those tanks, but don't know if it came with the tank or you found your own. I posted a pic on the HAMB once, but haven't tried any pictures of anything here yet.

 

[Beerhippie]

-This is a WAG so don't put too much credibility in it. Sometimes an oddball size can either mean it was an individual project and that's what was on hand to finish the project. Or it was an attempt at capturing business by using a proprietary/oddball item that was only available from one source, theirs. The use of proprietary/oddball thread designations (TPI or thread form) was encountered now and then, especially on expensive equipment.

Don't forget outdated standards. Too often I see folks just assume that a thread or fastener size is "proprietary" when it's just from an older system.

One example would be the valve thread size on older Coleman lanterns and stoves. It's 1/2 X ?tpi, tapered, but not any NPT standard. Even on the Coleman Collector's Forum, you'll often see this referred to as a proprietary thread. But it's also the same threading found on numerous makes of gasoline plumber's blowtorches and some propane/NG appliances from the same era, so NOT proprietary. I don't know just what standard it is, but it was a standard at one point. Before anyone suggests it, it isn't the American Dryseal thread (NPTF or NPSM) standard, either.

 

[RoninB4]

Don't forget outdated standards. Too often I see folks just assume that a thread or fastener size is "proprietary" when it's just from an older system.

One example would be the valve thread size on older Coleman lanterns and stoves. It's 1/2 X ?tpi, tapered, but not any NPT standard. Even on the Coleman Collector's Forum, you'll often see this referred to as a proprietary thread. But it's also the same threading found on numerous makes of gasoline plumber's blowtorches and some propane/NG appliances from the same era, so NOT proprietary. I don't know just what standard it is, but it was a standard at one point. Before anyone suggests it, it isn't the American Dryseal thread (NPTF or NPSM) standard, either.

-A good posting. I purposely used the word proprietary because it would be understood by most. To include/cite the lesser known and older thread systems might have caused further confusion or brought questions like "why?" that I had neither an explanation or an example for. Just the threads listed in Machinery's Handbook alone are plenty without all the thread designations that are non-standard, "obsolete", or proprietary. Appreciate you posting some examples/applications that illustrate that point. Before standards were established manufacturing was sometimes a very messy affair. Thanks for posting.

 

[Beerhippie]

-A good posting. I purposely used the word proprietary because it would be understood by most. To include/cite the lesser known and older thread systems might have caused further confusion or brought questions like "why?" that I had neither an explanation or an example for. Just the threads listed in Machinery's Handbook alone are plenty without all the thread designations that are non-standard, "obsolete", or proprietary. Appreciate you posting some examples/applications that illustrate that point. Before standards were established manufacturing was sometimes a very messy affair. Thanks for posting.

And AFTER standards were adopted, whey changed several times before arriving at the DIN, JIS and SAE we usually use today.. plus a few other just to keep us on our toes.

This kind of relates to the "What do you use a 19/32" socket for" thread in GT forum. USS bolts and nuts.

 

[MShaw]

I remember when I was using Brown & Sharpe equipment years ago I complained that B & S used mongrel threads. The B & S rep said "no , we had a system that was fully documented and 30 years later the US came along with their mongrel system". Point of view is everything.

 

[OccupantRJ]

Don't forget outdated standards. Too often I see folks just assume that a thread or fastener size is "proprietary" when it's just from an older system.

One example would be the valve thread size on older Coleman lanterns and stoves. It's 1/2 X ?tpi, tapered, but not any NPT standard. Even on the Coleman Collector's Forum, you'll often see this referred to as a proprietary thread. But it's also the same threading found on numerous makes of gasoline plumber's blowtorches and some propane/NG appliances from the same era, so NOT proprietary. I don't know just what standard it is, but it was a standard at one point. Before anyone suggests it, it isn't the American Dryseal thread (NPTF or NPSM) standard, either.

We had a thread of 5/16-27 for liability reasons on one of the handheld torches we manufactured before I retired. This hopefully prevented customers from cobbling standard pipe fittings together for some “project”.

 

[OccupantRJ]

I remember when I was using Brown & Sharpe equipment years ago I complained that B & S used mongrel threads. The B & S rep said "no , we had a system that was fully documented and 30 years later the US came along with their mongrel system". Point of view is everything.

Some of the bolt threads on B&S were 1/2-12, used before the 1/2-13 days. When I worked on the machines, all bolts went into containers to keep from losing one.

 

[RoninB4]

We had a thread of 5/16-27 for liability reasons on one of the handheld torches we manufactured before I retired. This hopefully prevented customers from cobbling standard pipe fittings together for some “project”.

-Yep, liability was another reason for "unique" threads.

 

[Beerhippie]

We had a thread of 5/16-27 for liability reasons on one of the handheld torches we manufactured before I retired. This hopefully prevented customers from cobbling standard pipe fittings together for some “project”.

And that's what NPT taps and dies are for!

 

[RoninB4]

And that's what NPT taps and dies are for!

-Scandalous

 

[BillK]

How are you measuring it ? Probably unlikely but could it be Metric ? 16.5mm is pretty close.

A couple of pictures would be nice.

 

[Leon bee]

I used calipers, but then went and got my good micrometer. .652 something. I'll take my camera out to the shop.

 

[RoninB4]

I used calipers, but then went and got my good micrometer. .652 something. I'll take my camera out to the shop.

-Do you know how to use paper to clean the anvil/spindle faces before "zeroing" your mic? Just asking.

A reading of .652=16.56mm and that sounds uncommon. I suppose oversized metric shafting is possible, it's available here in the US, but it's even uncommon here in the US. Sounds even more unlikely for something that was in production of some sort. JMO

 

[BillK]

Is this what you are working on ?

WWII WW2 Bomber Air Oxygen Tank Air Compressor - Vintage Kit?? | eBay

Found in an old truck headed for the crusher. Looks to be missing the piece(s) that would connect to an air hose. One aluminum leg has been (badly) welded back together. Base of motor is cracked so motor is sitting a bit wonky.

www.ebay.com

 

[Leon bee]

Is this what you are working on ?

Wow! Bill K., now that makes the second one of those I've ever seen. Mine is a different version, though. Mine has cast pieces like that to hold the tank, but is a wheeled version with pulling handle. A similar pump, but different. Maybe I can link to a picture I posted on the HAMB, will check on that.

 

[Leon bee]

Ronin: I have one of those little fraction charts on the shop wall, my measurement pretty much matches 21/32".

 

[Provincial]

There are three different 7/16" grease hose fitting threads. 20, 27, and 28 threads per inch. Some manufacturers use two of the three.

 

[Leon bee]

Have to go get on a real computer where I have photos from my real digital camera. Smartphones and goooglebook laptops ain't always the simple way to live.

 

[Leon bee]

..

 

[leg17]

Looks like two choices.
If you are taking the pump apart, turn down the end of the shaft to 5/8.
If not, open the pulley to fit.
Gonna need a machinist either way.

 

[BillK]

It looks like the pulley has a split hub on it with a bolt to clamp it tight. That might explain the oddball size. If there is not a keyway on the shaft you might have to do the same thing. Machining the center of the pulley would be a very simple job with a large enough lathe. Here is another one from the Jalopy Journal :

https://www.jalopyjournal.com/forum/threads/this-weeks-score-just-an-old-compressor.1017524/

 

[Leon bee]

I got my little compressor restoration going. Thinking red wheels:

 

[rancherbill]

The little pump could be war surplus, it looks like it says "T.P. CO. MADE IN USA". Guess we can ream out a 5/8 pulley hub, but I'm curious if anybody has an idea about this. Thanks!

The US built planes for the British and Allies. I imagine they were all the same for the spare parts issue.

 

[Leon bee]

Little compressor coming along. Collecting parts to plumb it, I'm unsure about the red wheels: